Rashid Khan
75 lines
2.4 KiB
Markdown
75 lines
2.4 KiB
Markdown
# Random Weighted Choice
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[](http://travis-ci.org/parmentf/random-weighted-choice)
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Node.js module to make a random choice among weighted elements of table.
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## Installation
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With [npm](http://npmjs.org) do:
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$ npm install random-weighted-choice
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## Examples
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Although you can add several times the same id
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var rwc = require('random-weighted-choice');
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var table = [
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{ weight: 1, id: "item1"} // Element 1
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, { weight: 1, id: "item2"} // Element 2
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, { weight: 4, id: "item3"} // Element with a 4 times likelihood
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, { weight: 2, id: "item1"} // Element 1, weight added with 2 => 3
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];
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var choosenItem = rwc(table);
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var choosenUnlikely = rwc(table, 100); // The last shall be first
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var choosenDeterministically = rwc(table, 0);
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It is better to not use the same twice, if you want a temperature other than
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the default one (50).
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var rwc = require('random-weighted-choice');
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var table = [
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{ weight: 1, id: "item1"} // Element 1
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, { weight: 1, id: "item2"} // Element 2
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, { weight: 4, id: "item3"} // Element with a 4 times likelihood
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, { weight: 2, id: "item4"} // Element 4
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, { weight: 2, id: "item5"}
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];
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var choosenItem = rwc(table);
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var choosenUnlikely = rwc(table, 100); // The last shall be first
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var choosenDeterministically = rwc(table, 0);
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Without temperature (second parameter) or a 50 value, likelihoods are:
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{ item1: 10%, item2: 10%, item3: 40%, item4: 20%, item5: 20% }
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With a temperature value of 100:
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{ item1: 30%, item2: 30%, item3: 0%, item4: 20%, item5: 20% }
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With a temperature value of 0, modified weights are:
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{ item1: 0, item2: 0, item3: 8, item4: 2, item5: 2 }
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## Usage
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### random-weighted-choice(Array table, Number temperature = 50)
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Return the ``id`` of the chosen item from ``table``.
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The ``table`` parameter should contain an Array. Each item of that Array must
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bean object, with at least ``weight`` and ``id`` property.
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Weight values are relative to each other. They are integers.
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When the sum of the weight values is ``null``, ``null`` is returned (can't choose).
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When the Array is empty, ``null`` is returned.
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More explanations on how it works on [Everything2](http://everything2.com/title/Blackboard+temperature).
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## Also
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* https://github.com/Schoonology/weighted |